KR100875164B1 - Method for cleaning wafer - Google Patents

Abstract

The method of cleaning the wafer is provided to prevent the imperfect formation of silicide due to residues in the silicide forming process and to prevent the yield loss of the silicide formation due to the residues. The method of cleaning the wafer comprises as follows. The step is for removing the first residues remaining on the surface on which the mixture will be formed by using the sulphuric acid, the second mixed cleaning liquid and first mixed cleaning liquids. The step(40) is for removing the oxide film remaining on the surface by using the diluted hydrofluoric acid washing liquid. The step is for removing the second residue including the particle caused in the removal process of the oxide film by using the first mixed cleaning liquid. The first mixed cleaning liquid is the washing solution which mixed with the ammonia, and the hydrogen peroxide and water. The second mixed cleaning liquid is the washing solution which is mixed with the hydrochloric acid, and the hydrogen peroxide and water.

Description

Method for cleaning wafer

1 is a flowchart for explaining a wafer cleaning method according to the present invention.

2 shows an exemplary cross-sectional view of a general semiconductor device for aiding in understanding a method of cleaning a wafer according to the present invention.

3 (a) and 3 (b) are diagrams showing the appearance of silicides having defects formed by the conventional wafer cleaning method.

* Explanation of symbols for main parts of the drawings

50 substrate 51 device isolation film

52 gate insulating film 54 gate electrode

56: lightly doped region 58: halogen ion implantation region

62: gate spacer 64: source / drain region

66, 68: silicide

TECHNICAL FIELD The present invention relates to cleaning, and in particular, to a method for cleaning a wafer.

As the density of semiconductors increases dramatically, the surface resistance (RS) is high because all of the sources / drains or gates that are in contact with the metal through contacts are silicon states. In particular, the polysilicon of the gate has a very high surface resistance of 5 to 40? / Sq. Therefore, in order to improve the driving speed of the chip, the surface resistance of the portion where the junction and the metal wiring are connected must be lowered. Due to the high resistivity, polysilicon increases the sheet resistance, which causes the time constant (RC) delay, which acts as a limiting factor for the increase in integration.

Research into metal silicides that can reduce the surface resistance of junctions in contact with metals with new wiring materials that can lower the resistivity while maintaining the properties and thermal stability of polysilicon. After forming a polysilicon gate and forming a gate sidewall spacer to separate the gate and the junction, titanium (Ti) or cobalt (Co) is deposited by a sputter method. Subsequently, when a rapid thermal process (RTP) is performed, silicide (TiSi2 or CoSi2), which is a compound having a small surface resistance, is formed by the reaction of metal only at a portion where Ti or Co is in contact with silicon. In this case, when the wet etching solution is treated, only Ti or Co, which is not reacted with no silicide, is selectively removed from the upper surface of the insulating layer such as side well spacers. Subsequently, the silicide may be annealed. The silicide formation method that does not require patterning as described above is called salicide (Self Aligned Silicide). At this time, while maintaining the advantages of the low specific resistance value, which is a unique feature of the silicide using Co, the impurities implanted in the substrate are diffused to improve the characteristics of the contact resistance and conductivity, thereby forming the secondary phase (CoSi2). And the secondary phase formed causes problems that can increase the surface roughness and increase the contact resistance.

An object of the present invention is to provide a method for cleaning a wafer which can increase the yield by smoothly cleaning the residues remaining on the surface of the wafer on which the metal reacts in the wafer to form a mixture. .

In the cleaning method of the wafer according to the present invention for achieving the above object, the sulfuric acid cleaning liquid, the second mixed cleaning liquid and the first mixed cleaning liquid in order to replace the first residue remaining on the surface where the metal is reacted to form a mixture in the wafer Removing the oxide film remaining on the surface by using a diluted hydrofluoric acid cleaning solution, and mixing the first residue with a second residue on the wafer and including particles generated upon removal of the oxide film. The cleaning solution comprises a step of removing using a cleaning solution, wherein the first mixed cleaning solution is a cleaning solution in which ammonia, hydrogen peroxide and water are mixed, and the second mixed cleaning solution is a cleaning solution in which hydrochloric acid, hydrogen peroxide and water are mixed.

Hereinafter, an embodiment of a wafer cleaning method according to the present invention will be described with reference to the accompanying drawings.

1 is a flowchart for explaining a wafer cleaning method according to the present invention. 2 shows an exemplary cross-sectional view of a general semiconductor device for aiding in understanding a method of cleaning a wafer according to the present invention.

Prior to describing the wafer cleaning method according to the present invention illustrated in FIG. 1, one example of general semiconductor devices to which the wafer cleaning method may be applied will be described below with reference to FIG. 2. The semiconductor device shown in FIG. 2 is merely an exemplary diagram for aiding in understanding the wafer cleaning method according to the present invention shown in FIG. 1, but the present invention is not limited thereto.

Referring to FIG. 2, the device isolation layer 51 defines a device region where a device is to be formed and an active region for separating the device on the substrate 50. The gate insulating film 52 is formed on the substrate 50, and the gate electrode 54 is formed on the gate insulating film 52. Lightly doped drain (LDD) regions 56 are formed in active regions below both sides of the gate electrode 54, and a halo ion implantation process is performed to form halo ion implantation regions 58. In addition, a gate spacer 62 is formed on the side of the gate electrode 54. The source / drain regions 64 are formed through a high concentration ion implantation process. In addition, silicide 68 is formed on the gate electrode 54, and silicide 66 is formed on the source / drain region 64.

1 and 2, after the gate spacer 62 is formed on the side of the gate electrode 54 on the substrate 50 of the wafer (not shown), ashing is performed (step 32). ).

After the thirty-second step, the first residue remaining on the surface of the wafer where the metal is reacted to form the mixture is removed using at least one of the sulfuric acid cleaning solution and the first and second mixed cleaning solutions (steps 34 to 38). field). The surface on which the metal reacts in the wafer to form the mixture may mean a contact surface such as the surface of the gate electrode 54 and the surface of the source / drain region 64 shown in FIG. 2. The metal may be cobalt (Co) or titanium (Ti) or the like to form a mixture, and the mixture may be salicide formed by the salicide method by cobalt or titanium.

In other words, the first residue is removed using a sulfuric acid cleaning solution (step 34). Here, the first residue that can be removed by the sulfuric acid cleaning solution means a residue of the photosensitive film remaining after the ion implantation. 2, high concentration ion implantation for forming the source / drain region 64, low concentration ion implantation for forming the LDD region 56, and / or halo ions for forming the halo ion implantation region 58. Residue remaining on surfaces 54 and 64 may be removed by sulfuric acid cleaning liquid by injection or the like. Here, the sulfuric acid washing solution refers to a washing liquid a mixture of sulfuric acid (H ₂ SO ₄₎ and hydrogen peroxide (H ₂ O _2). For example, a thirty-fourth step may be performed by dipping the wafer in a sulfuric acid cleaning solution having an ambient temperature of 85 to 115 ° C. for about 5 to 10 minutes. Sulfuric acid cleaning solution has excellent removal rate of residues such as photoresist film, but cannot remove defects in which metal compound is present on the surface by the metal used for implanting impurity ions such as Asonic.

Accordingly, the first residue such as the impurity ion metal remaining on the surface not yet removed in step 34 is removed using the second mixed cleaning liquid SC2 (where SC is Standard Clean). ). The second mixed cleaning liquid SC2 is a cleaning liquid obtained by mixing hydrochloric acid (HCI), hydrogen peroxide, and water (H ₂ O), and may have an ambient temperature of 20 to 30 ° C.

After the 36th step, the first mixed cleaning solution SC1 at room temperature may be used to remove the first residues such as fine organics, fine inorganics, and particles that have not been removed on the surface (step 38). The first mixed cleaning liquid SC1 is a cleaning liquid in which ammonia (NH ₄ OH), hydrogen peroxide and water are mixed. For example, the 38th step may be performed by dipping the wafer into the first mixed cleaning solution having an ambient temperature of 20 to 30 ° C. for 5 to 10 minutes.

After the 38th step, the oxide film remaining on the surfaces of the portions 54 and 64 where the silicides 66 and 68 are to be formed is removed using a dilute hydrofluoric acid cleaning solution (step 40). Native oxide films or oxide residues remaining on the surfaces of the regions 54 and 64 where the silicides 66 and 68 are to be formed may be removed by the hydrofluoric acid cleaning liquid in step 40. In general, a buffer oxide is formed on the entire surface of the substrate 50 including the gate electrode 54, and the gate spacer 62 is formed by etching the entire oxide film. At this time, the oxide residue caused by the front vision can be removed in the forty step. The diluted hydrofluoric acid washing liquid means a washing liquid mixed with water and hydrofluoric acid (HF). For example, the 40th step may be performed by dipping the wafer into the cleaning liquid having an ambient temperature of 20 to 30 ° C. for 200 seconds. According to the present invention, the forty step of removing the oxide film using the hydrofluoric acid cleaning solution may be performed a plurality of times. For example, the wafer may be repeatedly dipped twice in 100 seconds in the aforementioned cleaning atmosphere.

After the forty-second step, the second residue, which is present on the wafer and includes the oxide particles, the inorganic and organic matter on the surface, or the water mark, which is caused upon removal of the oxide film, is removed by using the first hot cleaning solution. (Step 42). Since the 42nd step is performed, the formation of the residue may be suppressed. The atmospheric temperature at the time of cleaning the first mixed cleaning liquid of high temperature used when removing the second residue is higher than the ambient temperature at the cleaning of the first mixed cleaning liquid at room temperature used when removing the first residue. For example, the 42nd step may be performed by the first mixed cleaning liquid having an ambient temperature of 50 to 60 ° C. during the cleaning.

In the case of FIG. 1, a thirty sixth step is performed after the thirty-fourth step is performed, and a thirty-eighth step is performed after the thirty-sixth step is performed. However, the thirty-fourth to thirty-eighth steps may be performed in an unrelated order when removing the first residue. However, steps 34 to 36 are performed before steps 40 and 42.

Meanwhile, the wafer may be dried by a spin dryer (not shown) after the first and second residues are removed. Table 1 below exemplarily shows a cleaning time, a drying time, and a temperature at which the above-described 32nd to 44th steps are performed.

Cleaning solution Sulfuric acid HQDR SC2 HQDR Room temperature SC1 HQDR F / R S / D HF EDR High Temperature SC1 HQDR F / R S / D Temperature (℃) 100 ± 15 N / A 25 ± 5 N / A 25 ± 5 N / A N / A N / A 25 ± 5 N / A 55 ± 5 N / A N / A N / A Time in seconds 60 to 600 600 60 ~ 600 600 60-600 600 600 600 300 ~ 600 600 2350 600 600 600

Here, HQDR means Hot Quick Dump Rinse, F / R means Final Rinse, S / D means Spin Dryer Drying, and EDR means End Dump Wash. (End Dump Rinse), and N / A means not applicable.

The wafer cleaning method according to the present invention shown in FIG. 1 may be performed after forming a gate spacer on a substrate and before sputtering a metal such as cobalt or titanium to form silicide. However, the present invention is not so limited, and may be applied in any case to remove the first and second residues on the surface where the metal is sputtered.

3 (a) and 3 (b) are diagrams showing the appearance of silicides having defects formed by the conventional wafer cleaning method. The appearance of the silicide according to the pattern line is shown as shown in Fig. 3 (a) or 3 (b).

When the silicide is formed in the state where the first and second residues are present on the surface on which the silicide is to be formed, the silicide becomes flawed as shown in FIG. 3 (a) or (b). However, according to the present invention, before forming the silicide, the first and second residues remaining on the surface of the portion where the silicide is to be formed are removed through the 32 to 42 steps. Subsequently, even when the silicide is formed by the salicide method, the silicide does not have a defect as shown in Fig. 3 (a) or (b).

Above, preferred embodiments of the present invention described above are disclosed for the purpose of illustration. Accordingly, those skilled in the art will be able to make various other embodiments within the spirit and scope of the present invention as disclosed in the claims by way of improvement, modification, replacement, or addition of the disclosed embodiments.

As described above, in the wafer cleaning method according to the present invention, unlike the conventional method of cleaning the wafer using only the hydrofluoric acid cleaning liquid and the first mixed cleaning liquid, at least one of sulfuric acid cleaning liquid, room temperature first mixed cleaning liquid and second mixed cleaning liquid The wafer is further cleaned using to effectively remove the first and second residues remaining on the surface where the metal reacts in the wafer to form the mixture, for example the gate electrode and / or the source / drain regions where silicide is to be formed. It is possible to prevent the incomplete formation of the silicide due to the residue in the subsequent process, that is, the silicide formation process, thereby preventing the yield loss of silicide formation due to the residue.

Claims (14)

A method of cleaning a wafer having a gate electrode and a source / drain region, Removing the first residue remaining on the surface of the wafer on which the metal is reacted to form a mixture by using a sulfuric acid cleaning liquid, a second mixed cleaning liquid and a first mixed cleaning liquid in this order; Removing the oxide film remaining on the surface by using a diluted hydrofluoric acid cleaning solution; And Removing, using the first mixed cleaning liquid, a second residue present on the wafer and containing particles caused upon removal of the oxide film; And the first mixed cleaning solution is a cleaning solution in which ammonia, hydrogen peroxide and water are mixed, and the second mixed cleaning solution is a cleaning solution in which hydrochloric acid, hydrogen peroxide and water are mixed. The cleaning atmosphere of claim 1, wherein the ambient temperature during cleaning of the first mixed cleaning solution used to remove the second residue is higher than the ambient temperature during cleaning of the first mixed cleaning solution used to remove the first residue. The cleaning method of the wafer characterized by the above-mentioned. The method of claim 1, wherein the wafer is cleaned. And after removing the first residues, the removing of the oxide film and the second residues is performed. delete The method of claim 1, wherein the removing of the oxide layer using the hydrofluoric acid cleaning solution is performed a plurality of times. The method of claim 1, wherein the wafer cleaning method is performed after forming a gate spacer on a substrate of the wafer and before forming the mixture on the surface. The method of claim 1, wherein the ambient temperature during the cleaning of the diluted hydrofluoric acid cleaning solution is 20 to 30 ° C. The method of claim 1, wherein the ambient temperature during the cleaning of the first mixed cleaning liquid used to remove the second residue is 50 to 60 ° C. 3. The method of claim 1, wherein the ambient temperature during the cleaning of sulfuric acid and hydrogen peroxide in the sulfuric acid cleaning solution is 85 to 115 ° C. The method according to claim 1, wherein the ambient temperature during the cleaning of the second mixed cleaning liquid is 20 to 30 ° C. The method of claim 1, wherein the ambient temperature during the cleaning of the first mixed cleaning liquid used to remove the first residue is 20 to 30 ° C. The method of claim 1, wherein the mixture corresponds to a silicide formed in at least one of the gate electrode and the source / drain region. The method of claim 1, wherein the wafer is cleaned. And drying the wafer by a spin dryer after the first residue is removed. The method of claim 1, wherein the wafer is cleaned. And drying the wafer by a spin dryer after the second residue is removed.

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